Google hasn't changed the Page Rank trend like after every three months in a year and change its regulation often. On November 2011 Google had changed Page rank. Which were the huge Page Rank (PR) update of the year 2011 and now 2012 has begun and many webmaster web owners are waiting for the forthcoming Google PR update and anticipating the positive PR at begin of year 2012.
Not a single person knows the accurate frame, date and time when next Google PR update happen but the expected PR update period which we have observed form last two to three years are quite similar in timing so we can also expect the same period of Google PR update in 2012.
1- Google Page Rank (PR) Update of 2012:
Between 30 January, 2012 to 2 February, 2012 2-
2- Google Page Rank (PR) Update of 2012:
Between 30 June, 2012 to 2 July, 2012 3-
3- Google Page Rank (PR) Update of 2012:
Between 30 September, 2012 to 2 October, 2012 4-
4- Google Page Rank (PR) Update of 2012:
Between 31 December, 2012 to 3 January, 2013
Above referred Google Page Rank (PR) update dates are compulsory but, Google can also make little updates between those dates in 2012.